cacl2 treatment for fruits vegetables

8/12/2019 CaCl2 Treatment for Fruits Vegetables

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Calcium Chloride Treatment of Fruits and Vegetables

By

Suren Mishra, Ph.D.

Tetra Technologies, Inc.

25025 I-45 North

The Woodlands

Texas 77380

Executive Summary:

Calcium Chloride is proving to have a significant impact on the shelf life of various fruits

and vegetables. The benefits of applying calcium chloride to select fruits and vegetablesinclude:

Delays aging or ripening.

Reduces post-harvest decay.

Controls the development of many physiological disorders.

Increases the calcium content, thus improving their nutritional value.

The application of calcium chloride on the following fruits and vegetables has had theindicated results:

Apples:

retains fruit firmness

increases Vitamin C content decreases storage breakdown and rot

Strawberries and blueberries:

extends the shelf life

slows down the rate of decay

maintains the firmness of the fruit for extended periods

Peaches:

reduces their brown rotting and disease index

improves the quality

extends the shelf-life

Pears:

maintains firmness and freshness of slicedpearsfor extended periods

Oranges and pineapples:


improves the quality

Cantaloupe:



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Carrots:

improves the firmness


Tomatoes and mushrooms:

improves the firmness and quality

improves the shelf life Potatoes:

extends the storage life

improves quality of French fries

reduces the oil consumption

reduces the darkening

Introduction:

Early research into the effect of calcium on fruit and vegetable quality wasconcerned with calciums association with physiological disorders (DeLong, 1936).Subsequently, more than 30 calcium related disorders in various crops have beenidentified (Shear, 1975).It has been established that the disorders of storage organs offruits and vegetable appear closely related to low calcium content in tissues.

Pre- and post-harvest calcium applications have been used to delay aging orripening, to reduce post-harvest decay, and to control the development of manyphysiological disorders in fruits and vegetables (Poovaiah, 1986; Conway et al, 1994).Firming and resistance to softening resulting from addition of calcium have beenattributed to the stabilization of membrane systems and the formation of Ca-pectates,

which increase rigidity of the middle portion and cell wall of the fruit (Grant et al, 1973;Jackman and Stanley, 1995). This inhibits the degradation of the middle portion and cellwall (Buescher and Hobson, 1982) and improves the skin strength (Mignani et al., 1995).

Foliar application of calcium chloride has been reported to delay ripening andretard mold development in strawberries ( Cheour et al., 1990; Cheour et al., 1991) andraspberries (Montealegre and Valdes, 1993).

Post-harvest dips in calcium chloride solutions are also combined with heattreatment. Heat allows the formation of COO-groups from the pectin content of the fruitsor vegetables with which Ca2+ ions can form salt-bridge cross-links (Stanley et al, 1995).

This makes the cell wall less accessible to the enzymes that cause softening. This practicecontrols ripening, softening, and decay at the same time (Sams et al, 1993). Conway andSams (1984) have indicated that calcium enhanced tissue develops resistance to fungalattack by stabilizing or strengthening cell walls, thereby making them more resistant to

harmful enzymes produced by fungi, and that it also delays aging of fruits.

The demand for fresh-cut fruits and vegetables is growing, with an estimatedretail market of $11 billion (Anon, 1998). Although these products have met the


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consumers desire for convenience, product freshness and shelf life are still importantchallenges to the retailers. Use of calcium chloride for the treatment of fresh-cut fruitsand vegetables is potentially an attractive market.

Calcium dips have been used as firming agents to extend post-harvest shelf life of

a wide range of fruits and vegetables. Some of them are as follows:

apples (Abbott et al., 1989; Laurie and Klein, 1992; Mir et al., 1993;Sams et al., 1993)

strawberries (Garcia et al, 1996)

sliced cantaloupe (Luna-Guzman et al (1999)

sliced pears and sliced strawberries (Rosen and Kader, 1989)

sliced zucchini (Izumi and Watada, 1995)

blueberries (Camire et al., 1994)

peaches (Postlmayr et al, 1956)

tomatoes (Floros et al, 1992)

oranges (Potjewijd, et al, 1995; Pathmanaban et al, 1995; Vilas Boas etal, 1998)

pineapples (Boas et al, 1998; Goncalves et al, 2000)

Calcium can also reduce pathogen germination, sporulation and growth (Conwayet al., 1994) that are common in much root vegetable, like potato. This ultimately reducesthe storage decay of fruits or vegetables.

Apples:

Storage disorders of apples, such as water core, bitter pit, internal breakdown, andsoftening, have been reduced by post-harvest calcium chloride treatment (Bangerth et al.,1972; Mason et al., 1975; Reid and Padfield, 1975).

There are various ways calcium has been applied to apples. Pre-harvestapplication of calcium has the following effects:

Calcium sprays reduce storage losses (Sharples and Johnson, 1977;Drake et al., 1979).In a later publication (anon, 1995), Drake makesthe following statement: On delicious and Golden delicious apples,calcium sprays reduced the incidence of bitterpit and may also

diminish scald and internal breakdown three disorders that rendersome apples unmarketable. And in most instances, the firmness, total

acidity and juiciness rating of apples were improved by timelyapplications of calcium during the growing season

The amount of calcium taken into apples can vary from year to yearand by the degree of fruit maturity and the type of apple.


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Differences in growing condition, environmental factors, and fruitdevelopment can influence the amount of calcium uptake by fruits(Conway et al., 1994; Wojcik and Swiechowski, 1999). To increasecalcium concentration, foliar sprays should be conducted at late fruitgrowth stages (Wojcik, 2001).

A minimum of 3 sprays applied at monthly intervals beginning inMay or June are usually required to achieve control (Cparile, 2001).Fore more severe calcium deficiency cases, shorter treatment intervals(every 2 weeks) over the same 3-month period are recommended.Early treatment, when the fruits are about 1-inch size may be moreeffective in varieties (including Granny Smith, Golden Delicious,Mutsu, Gravenstein, Yellow Newtown, Jonathan and Red Delicious)that are very susceptible to bitter pit due to calcium deficiency.

Ferguson (2001) states Maximizing calcium concentration in apple

fruit, without incurring damage, will reduce risk of disorders and helpin maintaining firmness and other desirable quality properties. Heemphasizes the need to concentrate on the fruit on the tree in efforts toincrease post harvest quality, and goes on to recommend calciumchloride being the most effective source of calcium. He further pointsout that calcium nitrate is an effective source of calcium but its usecan cause russet problems later in fruit development.

Post-harvest applications have the following effects:

It increases calcium content of the apple tissues, which reduces thepostharvest decay (Conway, 1982; Conway and Sams, 1983).

Direct application of calcium is considered to be the best method ofincreasing flesh calcium content.

Dipping apples in CaCl2 solution can increase the calcium content oftissues (Bangerth et al, 1972).

Active infiltration procedures, such as vacuum or pressure that forcesolutions into fruit are more effective in controlling bitter pit (Scott

and Wills, 1979).

Conway and Sams (1983) treated Golden Delicious apples for 2min. with 0 to 12% CaCl2solutions by dipping , vacuum infiltration(4.83 psi) or pressure infiltration (10 psi). Over the range of CaCl2treatment solutions, dipping (250 to 700 mg Ca/kg dry weights) wasleast effective in increasing the calcium concentration of the tissue.Vacuum infiltration (250 to 1500 mg Ca/kg dry weight) was superior


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to dipping, but pressure infiltration was most effective (250 to 3250mg Ca/kg dry weight) in increasing the calcium concentration in appletissues.

Calcium treatment help to retain fruit firmness (Table 1), increases

Vitamin C content (Table 2), and decreases storage breakdown and rot(Poovaiah, 1986; Conway and Sams, 1984).

A single post harvest dip of calcium chloride, in place of in-seasonsprays, has been effective on some varieties, including Granny Smithand Yellow Newtown, but not on Mutsu and others (Cparlie, 2001). A1-minute dip in 2% (for Yellow Newtown) or 3% (for Granny Smith)solution has typically been used. Dip time and the concentration ofcalcium chloride solution should be carefully tested on individualfruits, as higher dip time and concentrations can lead to fruit damage.

Table 1

Relationship between peel and flesh calcium content and fruit

Firmness in Golden Delicious apples infiltrated with 3-4% calcium

Chloride (after Poovaiah, 1986)

Results after 90 days of storage

at 32oF

Calcium Content Fruit Firmness*

(mg/kg) (lb)

Treatment Peel Flesh

Control (without CaCl2) 890 190 12.20

350 mm Hg (6.77 psi) 1,442 287 13.27with CaCl2

250 mm Hg (4.83 psi) 1,642 359 14.72with CaCl2

*Initial fruit firmness at harvest time was 16.58 lb


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Table 2

Effect of calcium infiltration on Ascorbic Acid content in

Golden Delicious apple. Fruits were vacuum infiltered with

calcium chloride soon after harvest and stored at 32oF

prior to analysis (after Poovaiah, 1986)

Ascorbic Acid Content

(mg/kg dry wt.)

Treatment Week 0 3 6 9 12 15

Control 140 125 130 120 135 130

Water 140 127 132 130 120 130

2% CaCl2 140 148 172 180 160 158

4% CaCl2 140 146 165 220 235 228

Strawberries:

It is one of the most readily perishable fruits. Garcia et al (1996) havedemonstrated that the post-harvest dip in calcium chloride reduced strawberry decayduring shelf life. The treatment with 1% solution of calcium chloride at 77oF was noted tobe most effective. Test data are summarized in Table 3.

Table 3Effect of Calcium Chloride Dip on Strawberries

(after Garcia et al., 1996)

Rotted Fruits (%) Fruit Firmness (N/cm2)

Control 1% CaCl2 Control 1% CaCl2

Shelf Life*at 3 days and 64.4oF 100 35 6 15

N (Newton) = 0.22481 lb

*Prior to this shelf life test, strawberries were submerged in a 1% CaCl2solutionat 77

oF for 15 minutes and stored for 1 day at 33.8

oF.

Garcia et al (1996) have noted the following:

Fruits that were dipped in 1% CaCl2solution at 77oF had significantly

higher concentration of calcium content than the control.

However, the calcium content of these fruits was significantly lowerthan that of fruits dipped in 1% CaCl2solution at 113

oF.


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The calcium contents for the control, 1% CaCl2at 77oF and 1% CaCl2

at 113oF were reported to be about 0.28%, 0.38% and 0.54%,

respectively of the fruit on the dry weight basis.

This increase in the calcium content by about 36% and 37% at 77oF and 113

oF,

respectively, could also be considered nutritional value that has been added to the fruit

Table 4

Effect of CaCl2Dips on Firmness (Relative Shear Force)

of G-3 Strawberries Stored at 36.5oF for 7 Days and

at 68oF for 1 Day(after Rosen and Kader, 1989)

Day 0 Day 7 Day 8

Treatment Firmness Ca Firmness Ca Firmness Ca

(N) (mg/kg) (N) (mg/kg) (N) (mg/kg)

Water 52.2 103 47.1 114 47.3 110

0.5% CaCl2 54.3 167 56.3 167 53.4 168

1.0% CaCl2 53.4 214 57.0 231 56.7 228

No Dip,Freshly Sliced 51.4 101 48.9 104 53.7 107

Test data reported by Rosen and Kader (1989), as given in Table 4, show the

following:

Calcium chloride dips result in higher calcium content.

While initially there was little differences in the fruit firmness,after 7 days at 36.5oF, both 0.5% and 1.0 % CaCl2dips resultedin firmer fruit with higher calcium contents than either water-dipped slices or whole, freshly sliced fruit.

They also note that by increasing the CaCl2concentration from0.5% to 1.0 % the calcium content of the fruit slices increased,but their firmness value was not different.

After transfer to 68oF ( i.e. Day 8), the CaCl2treated slices

were as firm as whole, freshly cut sliced fruit, and they werefirmer than water-dipped slices.


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In a separate investigation, Morris et al (1985) have demonstrated the following:

Calcium treatment maintains firmness in sliced strawberrieseven better than what was noted to be in the case of wholestrawberries.

This could be attributed to more surface area being available for the adsorption of CaCl2when strawberries were sliced.

Peaches:

Similar to strawberries, peaches are highly perishable. A method of delaying theirripening would be of considerable value. On the basis of post-harvest treatment tests,Wills and Mahendra (1989) report the following:

Use of 1% calcium chloride at about 3 psi significantlyextended the time to ripen on 7 of the 9 groups of peachesexamined.

The average time to ripen at 68oF in all 9 groups was extendedfrom 11.1 days to 14.4 days.

This increase in ripening time by about 30% is of significant commercial value.

Souza et al (1999) have shown the following:

Post-harvest application of calcium chloride at the site of injury

in peaches that had occurred during harvesting reduced theenzyme levels, and increased the levels of neutral sugar in thefruit.

It also reduced the brown rotting by about 34% and diseaseindex by about 29% as compared to untreated peaches.

From pre-harvest foliar applications of calcium chloride Robson et al (1989)conclude the following: This research shows that foliar applications of calcium to peachtrees throughout the growing season can have a positive affect on peach fruit quality in

storage. Calcium treated fruit maintained their quality longer than non-treated fruits.

Robson et al (1989) further states:A surprising result was the effect of calciumhad on the organoleptic acceptance of the fruit. Not only they were the Ca-treated fruit

rated superior in appearance, aroma, flavor, and texture after harvest, but this overallacceptance of the Ca-treated fruit continued to be greater than the control fruit even after

four weeks of storage.

On the basis of their pre-harvest treatment tests that involves application of 0.5%and 1.0% CaCl2solutions being sprayed on peach plants at pit hardening stage of the


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fruits, Mahajan and Sharma (2000) show the increase in size and improvement in qualityof the fruits. These treatments also enhanced the shelf life of the fruits. For thedetermination of the storage life, the fruits of different treatments were packed in woodenboxes and kept at room temperature. Selected test data are summarized in Tables 5 and 6.

Table 5Effect of Pre-harvest Application of Calcium Chloride

on the Quality of Peach

Treatment Length Diameter Weight Pulp-Stone Total Sugar

(cm) (cm) (g) Ratio (%) (%wt)

Control 4.5 4.1 49.8 4.0 5.00.5% 5.3 4.6 52.5 4.8 5.81.0% 5.5 4.9 54.5 4.9 6.1

Table 6

Effect of Pre-harvest Application of Calcium Chloride

on the Storage Life of Peach

Treatment PLW* (%) TSS** (%) Total Sugar (%)

Days 3 6 0 3 6 0 3 6

Control 10.5 28.0 10.0 12.5 9.7 5.0 5.8 4.30.5% 5.8 14.3 10.0 13.1 11.6 5.8 6.8 6.01.0% 5.3 13.2 10.8 13.7 12.0 6.1 7.2 6.6* Physiological Loss in Weight** Total Soluble Solid

As both strawberries and peaches are delicate fruits, to avoid physical damages,

precautions must be taken in their handling during the treatment process.

Pears:

Application of calcium to Anjou pear trees has been reported to have increasedyield by 13% over six year period (anon, 1995). It reduced the incidence of cork spot,which reduces the fruits intensity, keeping quality and market value. In the samepublication, it has been reported that on Bartlett pears, calcium sprays reduced black endor hard end abnormalities by more than 50%.

Rosen and Kader (1989) have demonstrated the effect of calcium chloride on thefirmness and calcium contents of the sliced pear, as shown in Table 7.


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Table 7

Effect of CaCl2Dips on Firmness of Bartlett Pears Stored at

36.5oF for 7 Days and at 68

oF for 1 Day (after Rosen and Kader, 1989)

Day 0 Day 7 Day 8Treatment Firmness Ca Firmness Ca Firmness Ca

(N) (mg/kg) (N) (mg/kg) (N) (mg/kg)

Water 45.4 78 20.0 73 15.1 68

1.0% CaCl2 49.4 206 35.1 158 28.0 189

No dip,Freshly sliced 45.4 73 27.1 68 20.9 61

Test data in Table 7 show the following:

1.0% CaCl2had an immediate firming effect on the slices,since they were significantly firmer than water-dipped slicesand whole, freshly sliced fruit.

The trend was consistent on Day 7 and Day 8.

They also report that CaCl2dipped slices of pears after 7 daysof storage at 36.5

oF were lighter in color than water-dipped

slices. This further confirms the reduction in the rate ofdegradation of pears when treated with calcium chloride.

From their studies Rosen and Kader (1989) have alsoconcluded that a combination of 1.0% CaCl2and 0.5% O2produces even greater maintenance of firmness than eithertreatment alone after return to air.

Similar to strawberries and peaches, pears are readily perishable fruit. CaCl2treatment

can be of considerable economic value to the producers or consumers.

Oranges:

With oranges, application of calcium chloride at the pre and post harvest stageshas shown to improve the quality of the fruit. Many investigators have studied the effectof pre-harvest application of calcium chloride on citrus fruits. Hsiung and Iwahori (1984)have found that calcium chloride treatment of Ponkan mandarin delayed its maturity.


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Schirra and Mulas (1994) have reported calcium chloride had retarded the maturity andimproved the storability of treated fruits.

El-Hammady et al (2000) have further confirmed the positive effects of calciumchloride on a citrus fruit that were earlier reported. This study was carried out on Balady

mandarin, in which the fruits in the trees were sprayed with 4 and 6% calcium chloridesolutions. Each treatment was replicated four times and the randomized complete blockdesign was followed. The treatments were done on the same day at the mature-greenstage of fruits, by spraying the trees in early morning with 5 liters (about 1.34 gallon) atthe selected concentrations of calcium chloride solution. Harvested fruits were stored at

5oC (41

oF) 1

oC and 90% Relative Humidity. Weight losses of the fruits and their

ascorbic acid content at different storage time intervals are summarized in Table 8.

Table 8

Effect of CaCl2Sprays on Weight Loss % and the Ascorbic Acid

Content (mg/100 g) of the Fruits (after El-Hammady et al, 2000)

% Weight Loss

Days in Cold Storage 15 30 45 60 75

Control 5.5 9.8 * * *4% CaCl2 2.0 3.2 4.3 5.3 6.56% CaCl2 2.0 2.8 3.2 4.4 5.8

Ascorbic Acid Content (mg/100g)

Days in Cold Storage 0 15 30 45 60 75

Control 42.7 40.7 32.3 * * *4% CaCl2 47.2 42.3 40.5 38.2 33.3 30.76% CaCl2 48.3 43.8 44.5 40.7 35.5 32.7

*Analyses were terminated after the decay of 50% of fruits

From a pre-harvest treatment of orange fruits in trees, Chikaizumi et al (1997)have reported that spraying oranges 6 times during the period of three weeks preventeddevelopment of disorders that occurs during post-harvest storage period.

Florida is the largest citrus fruit producing state in the United States. On-treevalue of Florida citrus crop is estimated at $1.1 billion. However, due to Floridas warmand humid climate, the disease problems of citrus in Florida are much greater than whatis encountered in many citrus producing areas of the country. California, though a verylarge citrus fruit producing state, does not have the same intensity of problems.


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Pineapples:

Pineapples grow and produce best where the temperature is warm and relativelyuniform throughout the year. Hawaii is the major producer of pineapples. In the mainlandUSA, although the climate of Florida is not ideally suited to large-scale commercial

production of pineapples, the state is a major producer of this fruit. Planting is restrictedto the southern coastal area. Major problems with the growing of pineapples are extremetemperatures. Prolonged exposure to temperature in the low 40s result in internalbreakdown or heart-rot of the flesh. On the other hand, extreme high temperaturescause sunburning and cracking of the fruit.

There are several varieties of fruit grown in Florida. In general the shelf life of theharvested pineapples allows them to be shipped to markets in different parts of thecountry. However, some fruits that are of superior eating quality, such as Alaska andPermambuco have a short shelf life. Any extension of their shelf life will improve theirmarketability.

Goncalves et al (2000) have reported that the post-harvest treatment of pineappleswith calcium chloride retards their decay rate. Harvested fruits of Smooth Cayennevariety (grown extensively in Florida) were soaked in calcium chloride solution atdifferent temperatures for different length of time. Fruits were stored at 9

oC (about 48

oF)

and 90% Relative Humidity for 15 days, and assessed 7 days after removal from thestorage. The samples that were treated with calcium chloride, regardless of temperatureand duration of treatment, reduced internal browning of the fruit. Calcium chloridetreatment also reduced the phenolics (indicative of decaying) content of the fruit. In anearlier publication Boas et al (1998) report the treatment of the same species of the fruitas described above resulted in adsorption of calcium species into the pineapple cell walls.This helped maintaining the level of pectic substances in the cell walls.

Melons:

Fresh-cut melons have become popular among consumers. Operations involved inthe preparation of fresh-cut melons may affect their shelf life, eating quality andacceptance by consumers. For fresh cut melons, a 10-day shelf life is considered to bedesirable in the distribution chain (Anon, 1996), but the retail stores get an average shelflife of only 3 days. Any improvement in their shelf life will substantially improve theretail profits.

Luna-Guzman et al (1999) have shown that calcium chloride treatment improvesthe firmness and the quality of freshly cut cantaloupes. A Texture Analyzer was used tomeasure the firmness of the melon slices. The melon quality or its metabolism wasevaluated in terms of the respiration rates (CO2production) and the ethylene productionrates of the freshly cut slices.


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Test results show the following:

Melon slices when treated with calcium chloride have reducedrate of change in the metabolism as has been indicated by thelower respiration rate.

Calcium chloride dips also improve the firmness of the freshlycut melons, and the calcium content of the fruit has been notedto be significantly greater than the control slices.

Temperature of the dip also has influence on the firmness of the slices.For example:

In the dip of 2.5% CaCl2 solution the respective firmness of thetreated slices for control, 68

oF, 104

oF and 140

oF was measured

to be about 5, 7, 8 and 9 N after the storage period of 4 days.

Treatment at 140oF the firmness of the melon slices wasmaintained at about the same level of about 9 N even after 12days of storage period.

Carrots:

Extending the earlier work of Bruemmer (1987) on carrot sticks showing that thecalcium treatment maintained the firmness for extended period, Izumi and Watada (1994)have studied the effect of calcium on the storage quality of sticks, sliced and shredded

carrots. Test results are summarized as Tables 9 and 10.

Table 9

Calcium Concentration of Carrot Slices, Sticks and Shreds

Treated with CaCl2 Solutions (after Izumi and Watada, 1994)

Treatment Cut Form Ca Conc.

(% CaCl2) (mg/kg dry wt.)

0 Shreds 20001 Slices 2300

1 Sticks 35001 Shreds 7400


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Table 10Calcium Concentration of Carrot Shreds

Treated with CaCl2Solutions (after Izumi and Watada, 1994)

Treatment Ca Conc.

(mg/kg dry wt.)

Control-water dip 20000.5% CaCl2 51001% CaCl2 7400

Test results in Tables 9 and 10 indicate the following:

By dipping carrots, sticks, slices or shreds, in calcium chlorideit increases their calcium content.

The greater calcium concentration in the shredded carrots could be attributed to thelarger surface area that is available for the adsorption of chemical.

From the study of the effects of calcium chloride dip on the weight loss andtexture of the carrot shreds, it is noted that the treatment substantially maintained theirquality during the storage period. For example:

At 32oF and 41

oF and storage period of 30 days, the % weight

loss and texture of the control and the treated shreds in 1.0 %CaCl2solution were noted to be as shown in Table 11.

CaCl2 treatment results in increased texture value by 69%(32oF) to 93% (41oF); and reduction in weight loss by about25% (41oF) to 60% (32oF).

Table 11

Effect of CaCl2Dip on the Texture and Weight Loss

of Shredded Carrots during Storage Period of 30 Days at 32oFand 41

oF

(after Izumi and Watada, 1994)

Texture Weight Loss

(N) (%)

(32

o

F) (41

o

F) (32

o

F) (41

o

F)

Control 2900 2700 5 41% CaCl2 4900 5200 2 3

N (Newton) = 0.22481 lb


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The total microbial count, a measure for the quality of carrots, was substantiallyreduced when the shreds were treated with 1% CaCl2 solution. The differential betweenthe control and the treated carrots, like the effects on the texture and weight loss, wasgreater at the extended period of storage. This inhibitory effect of calcium chloride isattributed probably to the increased resistance of tissues to the bacterial infection rather

than to a bactericidal action.

Tomatoes:

Calcium is a critical nutrient for the growth, quality and the shelf life of tomatoes.It is, therefore, needed for both pre and post-harvest applications to tomatoes.

While calcium application to the soil is essential for healthy growth of tomatoes,foliar application during the fruit growth period considerably improves the quality ofproduce. Subbiah and Perumal (1990) conclude the following:

Among the different sources and concentrations (calcium oxide, calciumchloride and calcium sulfate were included in the test), application of 0.2%sprays of CaCl2was found to be better to improve lycopene (responsible forthe color of the tomato fruit), ascorbic acid content and firmness index oftomato fruits.

In a later study Subbiah (1994) reports:Application of 0.5% CaCl2sprayssignificantly increased the firmness index of tomato fruits. He has also noted that thefirmness index was lowered by the increase in levels of added N. This behavior suggeststhat Ca(NO3)2may not be a desirable calcium source for such applications.

Hong and Lee (1999) have demonstrated the effect of infiltrated calcium onripening of tomato fruits. In this test, mature-green tomato fruits were vacuum-infiltratedwith 1 ml of 0, 2 and 8% calcium chloride and calcium nitrate solutions in distilled water.Vacuum infiltration was accomplished by applying ml of solution on the stem-scar,placing the fruit under 250 torr (4.834 lb/in.2) for 10 seconds and slowly releasingvacuum, allowing the solution to enter the fruit. They have concluded the following:

As ripening progressed, bound calcium content of control fruit decreased.

In contrast, fruits treated with 8% CaCl2or 8% Ca(NO3)2had increase in thebound calcium content.

Effect of calcium on firmness of mature-green tomato is shown in Table 10. Ascan been noted, increase in the concentration of CaCl2or Ca(NO3)2increases the firmnessof the fruit. However, test data indicate that the treatment with CaCl2produces greaterdegree of fruit firmness than Ca(NO3)2.


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Table 12Effect of Calcium on Firmness of Mature-Green

Tomato Fruit During Storage

Days after Firmness (N) after Treatment

Treatment Control CaCl2 Ca(NO3)2

2 % 8 % 2% 8 %

0 97.6 97.7 97.6 97.7 97.6

9 44.0 50.0 70.2 54.7 54.5

18 36.9 38.1 44.0 30.0 34.5

Mushrooms:

With steadily increasing consumption of fresh mushrooms, the demand forpremium quality product at the point of sale mainly focuses on whiter, firmermushrooms. In literature following claims have been made:

Applications ranging from 0.01 to 0.5% calcium chloride can affect thefollowing:

- Improve the color of fresh mushrooms (Beelman et al,1987; Burton, 2000), stored (Desrumaux et al., 2000)

- Improve the color of canned mushrooms (Kalberer,1991)

- Prolong their shelf life (Solomon et al., 1991; Mikulus

and Beelman, 1996).

From their studies Diamontopoulou and Philippoussis (2001) conclude thefollowing:

- 0.10% calcium chloride dose has beneficial effects onyield, size and improvement of mushroom firmness.

- Color improvement at the dosage of 0.25% calciumchloride.

These findings suggest that calcium chloride treatment could be used in thecommercial production of mushrooms to improve its quality, in terms of firmness and

their brightness.

Potatoes:

For potato, calcium has important roles to play at the various stages: growing,storage and the process stages. At the growing stage, calcium has the following effects:


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Reduction in decay depends on the amount of calcium presentin the tubers.

High calcium containing tubers are less susceptible to decay(McGuire and Kelman, 1984, 1986), and consequently could

be stored for a longer period of time.

Calcium application increases the calcium concentration in thetubers, and the incidence of internal defects was lower in thetubers that contained higher concentration of calcium(Kleinhenz et al., 1999)

Post-harvest and pre-storage treatment of potatoes with calcium is used to extendtheir storage life. One of themethods to firm up the tissues of potatoes is by heating it ata moderate temperature of 122

oF to 176

oF (Bartolome and Hoff, 1972). The firming

effect has been attributed to the following:

At temperature lower than 120oF the native pectin of the tissueis inactive.

At higher temperature free carboxyl groups are produced,which cross-link with the calcium or magnesium ions that arepresent in the cell interior, and render the tissue firmer.

This behavior has indicated that calcium as an additive could play a role in the firming of

potato tissues.

Walter et al. (1993) have shown that when strips of sweet potato were treated with

calcium chloride in conjunction with their treatment with Na2CO3, there were increasedfirmness in the strips. The process could be applied to other types of sweet potatoproducts ranging from dice to chunks.

Warren (1992) claims a process for treatment of freshly cut plant parts, whichextends the storage life of the parts. The process involves the following:

Dipping the plant parts in an aqueous solution that containedascorbic acid, citric acid, sodium polyphosphate and calciumchloride.

This treatment is claimed to extend the storage life of potatoes,

apples, pears and lettuce. In this patent, calcium chloride is being claimed to be an

enzyme inhibitor.

One of the major problems in the making of french fries has been the darkening ofthe final product. Calcium chloride can be used as darkening inhibitor.A combination ofgum acacia, gelatin and calcium chloride pretreatment is an effective method for theprevention of after-cooking darkening of french fries (Mazza and Qi, 1991).


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On the treatment of french fries with calcium chloride following furtherinformation is available in literature:

A treatment, which involved a single coating of potato frenchfries with a combination of 0.5 % calcium chloride and 5%pectin or sodium alginate, reduced the oil content of the friesby 40% (Khalil, 1999). French fries still retained high moisturecontent.

A second coating with 1.5% carboxy methyl cellulose (CMC)reduced the oil content by 54%.

This double coated french fries had higher moisture contentthan the single coated french fries.

Scanning electron microscope examination of these treatedfrench fries revealed that both single and double coatingprocess were effective in protecting the cellular structure ofpotato tissues from damage produced during deep-fat frying.

Market Information: United States produces about 23.75 million tons (1998Estimated figure) potatoes. Their major consumer usages are approximately as follows:

Fresh market 26%

Frozen products (mostly fries) 35%

Potato chips 11% Dehydrated products 12%

Calcium chloride treatment can be applied at the various stages of potatoproduction, post-harvest preparation and processing.

While potato production is spread out in the various parts of the country, Idahostill remains the largest producer followed by Washington, Oregon, Wisconsin andColorado.

Concluding Remarks:

It is clearly established that calcium deficiency has influence on the disorders ofstorage organs of fruits and vegetables. Post-harvest treatment or treatment at theprocessing stage extends their shelf life and also improves their quality. While calciumchloride can be used in a wide range of fruits and vegetable, market potential for apples,potatoes and some of the highly perishable fruits, like strawberries, peaches, pears,cantaloupe etc., is substantial.


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SkmUpdated 7/19/01

Revised 7/31/02

Revised 8/29/02


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cacl2 treatment for fruits vegetables

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